This invention relates to an intake manifold of an internal combustion engine, and more particularly to an intake manifold of an internal combustion engine in which a surge tank and an intake passage are positioned in a space defined by joining separable parts formed of synthetic resin having recesses, and a resonator in communication with the surge tank is provided in a simple divisional construction.
In an internal combustion engine having a plurality of cylinders as mounted on a vehicle, an intake manifold is disposed toward an intake side of the engine to introduce intake air to the cylinders. See JP Laid-Open No. H05-60023, JP Laid-Open No. H10-18849, and JP Laid-Open No. H10-339224
In a conventional intake manifold of an internal combustion engine, a surge tank and an intake passage are positioned in a space defined by joining separable parts formed of resin having recesses.
JP Laid-Open No. H10-18849 discloses an intake manifold of an internal combustion engine. The intake manifold of this publication includes a Helmholtz-type resonator comprising a resonance passage and a resonance chamber in the surge tank so as to improve output torque in a certain range for the internal combustion engine.
When such resonator is constructed by resinous divisional parts to form the intake manifold, it is typical that a separating member having a communication hole is disposed in the space to form the resonance passage and the resonance chamber, as disclosed in JP Laid-Open No. H10-339224.
However, if the resonance passage and chamber are formed in the above-mentioned manner, the volume of the resonance chamber is undesirably restrained by the surge tank or the intake passage.
Also, to improve the output torque in the low-mid range of the internal combustion engine by the resonator, the resonance passage is preferably formed to be longer in length. However, it is difficult to form the long resonance passage in the space in the separable parts by the separating member. Also, a joining section may be in a complex shape to join the separating member to the separable parts.
To obviate or at least minimize the above inconvenience, the present invention provides an improved intake manifold for an internal combustion engine. A first separable part includes an independent intake passage, a first recess, and a first joint section. The independent intake passage has a downstream open end connected to more than one intake port in the engine. The first recess is disposed on a side of the independent intake passage, and has an open end adjacent to an upstream open end of the independent intake passage. The first joint section surrounds the upstream open end of the independent passage and a periphery of the first recess. A second separable part includes a second joint section to abut the first joint section. This second part defines therein a second recess having an opened edge or circumference defined at the second joint section so that the second recess is disposed opposite to the independent intake passage. Intake air is sequentially introduced through the first and second recesses into the intake passage when the first and second separable parts are joined together. A communication hole is defined in the second separable part to communicate to outside. A third separable part covers the communication hole from outward. A resonator includes an outer wall defined by the second and third separable parts. The outer wall defines therein a resonator passage which communicates with the communication hole.
According to the present invention, the design of the volume of the resonator is more flexible. The third separable part is attached outward of the second separable part, which facilitates joining or mounting of the third separable part.